Antimicrobial susceptibility of gram-positive bacteria isolated in brazilian hospitals participating in the SENTRY Program (2005-2008)

ABSTRACT

We report the antimicrobial susceptibility patterns of the most frequently isolated Gram-positive bacteria in the Brazilian hospitals participating in the SENTRYAntimicrobial Surveillance Program. The strains were consecutively collected (one per patient) between January 2005 and September 2008 and susceptibility tested by reference broth microdilution methods at the JMI Laboratories (North Liberty, Iowa, USA). A total of 3,907 Gram-positive cocci were analyzed. The Gram-positive organisms most frequently isolated from bloodstream infections were Staphylococcus aureus (2,218 strains; 20.2 percent of total), coagulase-negative staphylococci (CoNS; 812 strains [14.7 percent]), and Enterococcus spp. (754 strains; 5.0 percent). S. aureus ranked first (28.1 percent) and Enterococcus faecalis ranked 7th (4.5 percent) among cases of skin and soft tissue infections. S. aureus was also the second most frequently isolated pathogen from patients with lower respiratory tract infections (24.9 percent of cases) after Pseudomonas aeruginosa (30.5 percent). Resistance to oxacillin was observed in 31.0 percent of S. aureus and the vast majority of oxacillin-resistant (MRSA) strains were also resistant to clindamycin, ciprofloxacin and levofloxacin. Vancomycin, linezolid and daptomycin were all very active against S. aureus strains tested (>99.9-100.0 percent susceptible), but daptomycin (MIC50, 0.25 g/mL and MIC90, 0.5 g/mL) was four- to eight-fold more potent than vancomycin (MIC50 and MIC90 of 1 g/mL) and linezolid (MIC50, 1 g/mL and MIC90, 2 g/mL). Vancomycin resistance increased significantly among enterococci during the study period, but it was restrict to only one medical center until 2007 and emerged in a second medical center in 2008. Daptomycin was the most active antimicrobial tested against enterococci in general (100.0 percent susceptible), followed by linezolid (99.9 percent susceptible), ampicillin (87.4 percent) and vancomycin (84.6 percent)...